Gear shifting device of a pneumatic transmission

Abstract

A pneumatic transmission for a motor vehicle is provided with a gear shifting device which comprises a first pneumatic cylinder mounted to a housing for moving a shift arm fixed to a shift shaft thereof in predetermined shift positions, and a second pneumatic cylinder mounted to the housing and arranged in a cross relationship with the first cylinder for moving the shift arm in predetermined select positions. The second cylinder includes a selector shaft and a select rod slidably disposed therein in an axially spaced opposite relationship with each other, and select arms extending from ends of the selector shaft and the select rod to converge toward an end portion of the shift arm. A yoke is provided to interlink the select arms with the shift arm so as to move the shift arm in the predetermined select positions through the clockwise and counterclockwise rotation of the shift arm by a linear movement of the selector shaft. The gear shifting device includes a valve assembly for actuating individually the first and the second cylinders.

What is claimed is: 
     
       1. A gear shifting device of a pneumatic transmission for a motor vehicle, which comprises: a housing;   a first pneumatic cylinder mounted to the housing, said first cylinder including a shift shaft slidably and rotatably disposed therein and a shift arm fixed to a portion of the shift shaft;   a second pneumatic cylinder mounted to the housing and arranged in a substantially cross relationship with said first cylinder, said second cylinder including a selector shaft and a select rod slidably disposed therein in an axially spaced opposite relationship with each other, and select arms extending from ends of the selector shaft and the select rod to converge toward an end portion of the shift arm, wherein each of said first and second cylinders includes a guide ring secured to each of the shift shaft and the selector shaft and located in a chamber thereof, a pair of separate pistons slidably interposed between an inner wall of each of the cylinders and the guide ring for dividing the chamber into two subchambers, and stoppers attached to the inner wall of each of the cylinders at a boundary of the subchambers for restricting the stroke of the pistons in the chamber;   a yoke for interlinking the shift arm of the first cylinder with the select arms of the second cylinder so as to convert a linear movement of the selector shaft into a clockwise and counterclockwise rotation of the shift arm, and   a valve assembly for actuating individually the first and the second cylinders, wherein the shift arm is moved in its predetermined select and shift positions by the individual actuation of the cylinders, said valve assembly including two sets of solenoid valves adapted to supply and discharge compressed air to and from the subchambers of the respective cylinders, and a regulator valve interconnected with one set of the solenoid valves in communication with the subchambers of the first cylinder for preventing an abrupt discharge of the compressed air from the subchambers of the first cylinder to atmosphere therethrough during the shifting operation of the device.   
     
     
       2. The gear shifting device of claim 1, further comprising contactless switch means provided at a cover of the housing and an upper portion of the shift arm for sensing a shifted state of the shift arm, wherein said predetermined shift positions of the shift arm define first to fifth forward speed positions and one reverse speed position, respectively, and said contactless switch means includes six lead switches attached to the cover for corresponding to the respective speed positions and a magnet fixed to the upper portion of the shift arm for facing one of the lead switches depending on the selective shifting operation of the device. 
     
     
       3. The gear shifting device of claim 2, wherein said yoke includes bolts passing through the select arms for allowing the shift movement of the shift arm therebetween, spacers mounted around the bolts for providing a clearance between the select arms and the shift arm, and nuts fixed to ends of the bolts.